Every drought, livestock operators increase their interest in buying, or harvesting and feeding straw. For grain producers, collecting straw means an additional harvest from otherwise droughty crops.
This brings up questions:
- What is the value of the straw?
- What nutrients are removed with the straw?
- Is all straw the same?
- Will baling and removing the straw hurt future crop yields from those fields?
The answer? It depends.
Let’s thresh out this subject into its components. How much is straw worth from a nutrient perspective? Again, it depends. Removing straw has one purpose, exporting nutrients out of a field. However, the straw’s nutrient content depends on the crop grown, the amount of residue on the field, the soil’s organic matter and fertility level.
When estimating the value of straw, farmers must first determine how much straw is being produced. Estimates can be made based on grain yield and plant height.
Then producers should determine how much straw is to be harvested from the field. This value will vary and depends on cutting height, combine type and how much of the straw is actually being baled.
Rotary combines may render straw of little value if combining occurs in dry conditions.
Many cattle feeders are reluctant to buy straw that has been combined with certain machine designs. As well, the impact of the combining method will be greater on barley and oat straw versus wheat straw.
What is the fertilizer value, in dollars per acre, of the straw being removed?
Removal of major nutrients, such as nitrogen, phosphorus and potassium, form much of the lost value to the grain field. Also, wheat straw contains calcium, magnesium, sulfur and a variety of micronutrients.
The amounts of those nutrients that are contained in the straws vary greatly.
Harvesting straw can accelerate soil-nutrient depletion rates and can cause deficiencies, specifically of micronutrients. Obtaining the weight of the bales harvested, ex-tracting a representative sample of the straw and having it analyzed for nutrient content, can provide a fairly accurate measure of the nutrients that were removed from the field.
Producers should also take into account the moisture content of the bale, and reduce the weight by this percentage, to get an actual, dry-matter figure.
The value of straw from winter wheat, spring wheat, oats and barley will largely depend upon the current market prices of nutrients being removed. For example, if a pound of nitrogen costs 70 cents, phosphorus 85 cents, potash 50 cents and sulfur 40 cents a tonne of oat straw will, on average, contain about $50 worth in nutrients. This true value will depend on fertilizer prices and the nutrient content of the straw, but basic calculations can provide a guideline.
While straw removal appears to be a nutrient robber, it probably won’t hurt future yields as much as many people suspect.
Results from long-term studies, where crop residues were removed through baling, provide valuable information as to the impact on soil quality and crop production.
Research at Indian Head, Sask., in the thin-black soil zone, showed no effects on spring wheat grain yields or on soil organic carbon and nitrogen after 30 years or 40 years of removal.
However, there may be some short-term impact. Much of the phosphate in crop residue is soluble and may feed the following crop early in spring. In areas where potash is at marginal levels of 100 parts per million or less, the removal of potash may also affect next season’s crop.
The removal of straw might prove to be a short-term benefit to nitrogen because if straw is left on the field and incorporated, it can immobilize nitrogen, which makes it unavailable to the crop. How much of an effect it has depends on the amount of straw incorporated, as well as the source and method of nitrogen application.
There is also a cost to managing your straw. Straw choppers take significant horsepower and there is wear and tear on the chopper and its knives.
Not collecting the straw might also mean another field operation, such as a heavy harrowing, for straw management, provided the drought hasn’t shortened the crop. Subtract these from the value of the nutrients removed through baling.
Producers who sell their straw should ask for a deposit, sometimes even from neighbours and family, to ensure timely baling and removal of the bales.
Nothing will sour a win-win relationship more than having a field full of bales that interfere with seeding the following spring.
- Adds organic matter to soil and can help improve structure.
- Returns nutrients to the soil.
- Potential to reduce nitrate loss.
- No structural damage to soil from baling and carting in wet conditions.
- No delay from baling and carting.
- Lower labour requirement, unless baling and carting is by contractor or buyer.
- Extra diesel used to chop straw.
- Extra operation may be required to spread straw.
- Potential to increase disease problems.
- Competition with crop for available soil nitrogen in spring.
- Possible incorporation difficulties on some soil types.
- No additional direct income.
Remove & sell straw
- Income from sale.
- Potentially easier and faster establishment of following crop.
- Possibly fewer disease problems.
- Costs of baling and hauling, unless purchased by contractor or buyer.
- Significant nutrient removal from field.
- Delays in baling and hauling may delay planting of following crop.
- Possible structural damage if soils are wet during baling and hauling.
- Income from sale of straw may not cover costs of operations and nutrients removed.
Thom Weir is an agronomist with Farmer’s Edge. He can be reached by emailing firstname.lastname@example.org.